Erik @airbum, the mystery is solved.
While perusing the AirCorps Aviation website this evening, I found a plethora of information for the UC-64, https://aircorpslibrary.com/aircraft/c-54-norseman-noorduyn. They just added this information over the past few days.
You may not be able to view them without a subscription, but here are some screen shots of the elusive "Escape Hatch" or "Emergency Exit" as the documents state. Apparently the AAC solicited a change in the design of the hatch operation mechanism.
I'm still not certain that all of the A/C purchased had this "Emergency Exit" since I have several photographs showing otherwise. Also take note, these documents clearly state this was on a UC-64 A model. I'll have to go back and look at the listing for A/C delivered to see if I can differentiate between which model the plane he was lost in was.
Another interesting tidbit, looking at the Erection Manual, it shows that the plane was lifted with a 4-point harness attaching to the upper side of the fuselage at the leading and trailing edges of the wings.
4 attached images. Click to enlarge.